1. Field of the Invention
This invention relates to a boat hull having a recess formed in the hull thereof for receiving a driveshaft, and more particularly, to a flow plate which substantially covers the recess to maintain the surface of the boat hull.
2. Description of the Related Art
A fairly recent development in boat design is the incorporation of tapered concave tunnels formed in the boat hull immediately adjacent to the propeller. Mounting a propeller near the end of a tapering, concave tunnel on the underside of a boat hull results in more efficient propulsion from the propeller for two reasons. First, the propeller is more efficient when it rotates in non-turbulent water and the tunnel provides more efficient water flow past the propeller. Secondly, more thrust is produced because of closer alignment of the longitudinal axis of the propeller shaft, i.e. the direction of force, and the desired direction of travel, i.e. forward along the horizontal plane of the water surface.
In one prior art design, the propeller shaft extends through the hull at an acute angle with respect to the bottom surface of the boat. A fiberglass tube is mounted on the inside of the hull and receives the shaft therein. A conventional packing member is mounted at the end of the tube to control the flow of water into the boat hull through the propeller aperture. This design suffers from the expense involved in installing the fiberglass tube, properly aligning the shaft and tube and repairing the tube following a grounding or other accident.
In another prior art design, the boat comprises an inwardly projecting recess formed in the bottom surface of the boat hull. An upstanding wall of the recess has a propeller aperture formed therein which receives the propeller shaft. The internal end of the shaft is mounted to an engine and the external end of the shaft has a propeller mounted thereto. The upstanding wall of the recess provides a substantially planar surface which is suited to receive the propeller shaft and provide a suitable mounting surface on the interior of the boat hull for packing material. The packing material surrounds the shaft and controls the flow of water into the hull through the propeller aperture.
A significant problem lies in the combination of the inwardly projecting recess in the boat and concave tunnels. Namely, the inwardly projecting recess is a disruption of the surface of the boat hull thereby resulting in the creation of turbulent water flow along the boat hull to the rear of the recess. Therefore, several of the benefits achieved in enhancing the substantially laminar flow along the underside of the boat hull with the concave tunnels is lost as a result of the turbulent flow created by the recesses.